wimboot

wimboot is a boot loader for Windows Imaging Format (.wim) files. It enables you to boot a Windows PE (WinPE) environment from a RAM disk, without wasting the memory used for the RAM disk image.

You can use wimboot with iPXE to boot Windows PE via HTTP. With a Gigabit Ethernet network, a typical 200MB WinPE image should download in less than two seconds.

Advantages

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Speed

wimboot can download images at the full speed supported by your network, since it can use HTTP rather than TFTP.

Efficiency

wimboot allows Windows to reuse the memory that was used to hold the RAM disk image; there is no wasted memory.

Ease of use

wimboot works directly with .wim image files; there is no need to wrap your .wim into an ISO or FAT filesystem image.

BIOS/UEFI compatibility

wimboot allows you to use a single procedure and set of files to boot under both BIOS and UEFI environments.

Download

You can download the latest version from http://git.ipxe.org/releases/wimboot/wimboot-latest.zip.

Older versions are available from http://git.ipxe.org/releases/wimboot. The source code is maintained in a git repository at http://git.ipxe.org/wimboot.git.

Getting started

If you have a Windows installation DVD-ROM (Vista, Server 2008, or more recent), and a web server (such as Apache or IIS), then you have everything you need to start using wimboot.

Extract the Windows boot files

A CD-ROM

Copy the contents of the Windows installation DVD-ROM to a directory on your web server (e.g. /var/www/win7 for Apache, or C:\inetpub\wwwroot\win7 for IIS).

If you do not have enough disk space to copy the entire contents of the DVD-ROM, then you may copy only the following files:

  /boot/bcd
  /boot/boot.sdi
  /sources/boot.wim

Download wimboot

Download the latest version of wimboot and extract the file wimboot to the same directory on your web server.

Create the iPXE script

Create a text file boot.ipxe in the same directory on your web server, containing:

  #!ipxe
  
  kernel wimboot
  initrd boot/bcd         BCD
  initrd boot/boot.sdi    boot.sdi
  initrd sources/boot.wim boot.wim
  boot

Boot

Boot using iPXE from the URL of your iPXE script, e.g. http://my.web.server/win7/boot.ipxe. You should see iPXE download your Windows boot files via HTTP and boot into the Windows installer:

wimboot booting Windows 7

Windows 7 installer booted via wimboot

Next steps

You can use wimboot to boot any bootable .wim image. See the Windows PE tutorial for information on how to create and customise your own .wim images.

Licence

wimboot is free, open-source software licensed under the GNU GPL.

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Advanced topics

Some books

Multi-image WIM files

A WIM file can contain multiple bootable images. You can use the index=<N> command-line option to select the image to be booted. For example:

  kernel wimboot index=2

Custom boot manager

wimboot will attempt to extract an appropriate boot manager (such as bootmgr.exe or bootmgfw.efi) from the WIM file.

You can disable this behaviour by explicitly providing an appropriate set of boot manager binaries. For example:

  kernel wimboot
  initrd bootmgr              bootmgr
  initrd efi/boot/bootx64.efi bootx64.efi

Disabling automatic BCD modifications

wimboot will automatically patch standard BIOS-compatible boot configuration data (BCD) files to allow them to be used on UEFI systems, by changing all occurrences of the string ”.exe” to ”.efi”.

You can disable this behaviour by using the rawbcd command-line option. For example:

  kernel wimboot rawbcd

Displaying graphical boot messages

wimboot will force the Windows boot manager to display error messages in text mode. It does this to work around a bug in some versions of the Windows boot manager, which would otherwise fail to display error messages unless suitable font files are provided.

You can disable this behaviour by using the gui command-line option and by providing all of the required font files. For example:

  kernel wimboot gui
  initrd boot/fonts/segmono_boot.ttf  segmono_boot.ttf
  initrd boot/fonts/segoe_slboot.ttf  segoe_slboot.ttf
  initrd boot/fonts/segoen_slboot.ttf segoen_slboot.ttf
  initrd boot/fonts/wgl4_boot.ttf     wgl4_boot.ttf

Troubleshooting

Try adding the commands imgstat and prompt to your iPXE script, to allow you to check that all of the files have loaded correctly. For example:

  #!ipxe
  kernel wimboot
  initrd boot/bcd         BCD
  initrd boot/boot.sdi    boot.sdi
  initrd sources/boot.wim boot.wim
  imgstat
  prompt
  boot

Check that only the expected files are present in the list. You may need to use the imgfree command to discard any unwanted files.

You can also try adding the pause command-line option for wimboot. For example:

  kernel wimboot pause

This will instruct wimboot to wait for a keypress before booting Windows, to give you a further opportunity to observe any messages that may be displayed.

If you are unable to resolve your problem, then you can contact the iPXE developers and other iPXE users.

 
wimboot.txt · Last modified: 2014/09/03 02:53 by mcb30
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